Groundbreaking MIT study challenges common assumptions about sleep

A recent study co-authored by MIT economists challenges the common assumption that getting more sleep leads to increased energy, emotional stability, and overall well-being.

The study, conducted in Chennai, India, focused on low-income workers and examined the effects of increased sleep on various aspects of their lives. Researchers conducted a field experiment to assess whether extending nightly sleep duration had a tangible impact on productivity, earnings, financial decision-making, well-being, and health.

Despite successfully increasing participants’ sleep by an average of half an hour per night, the study found no significant improvements in their work performance, earnings, or decision-making abilities. Additionally, there were no noticeable benefits for their overall well-being or blood pressure. The only measurable change was a reduction in the number of hours worked, suggesting that more sleep alone did not translate into meaningful positive outcomes.

What made this study unique was its focus on real-world conditions, as researchers observed participants in their homes rather than in a controlled lab environment. The findings highlight that while additional sleep is often believed to be beneficial, it may not automatically lead to better life outcomes, particularly if the quality of sleep remains poor. The results indicate that simply increasing sleep duration is not enough to enhance productivity or financial decision-making.

MIT economist and study co-author Frank Schilbach expressed surprise at the findings, stating, “To our surprise, these night-sleep interventions had no positive effects whatsoever on any of the outcomes we measured.” This challenges conventional wisdom about the benefits of extended sleep and suggests that other factors, such as sleep quality, may play a more critical role.

Interestingly, the research did find that short daytime naps had a positive effect on productivity and well-being. The study also noted that many participants faced disrupted sleep at night due to various external factors, making it difficult for them to achieve restful, high-quality sleep. These disruptions may have limited the benefits of simply increasing the total amount of sleep.

Schilbach emphasized that in environments like Chennai, where sleep quality is particularly poor, adding more low-quality sleep may not be as effective as improving sleep conditions. The study suggests that efforts to enhance the quality of sleep—rather than just its duration—could lead to more meaningful benefits for individuals in similar situations.

A paper titled "The Economic Consequences of Increasing Sleep Among the Urban Poor" has been published in The Quarterly Journal of Economics.

The authors of the paper include Pedro Bessone, who recently graduated from MIT’s Department of Economics with a PhD; Gautam Rao, an associate professor of economics at Harvard University; Schilbach, the Gary Loveman Career Development Associate Professor of Economics at MIT; Heather Schofield, an assistant professor in the Perelman School of Medicine and the Wharton School at the University of Pennsylvania; and Mattie Toma, a PhD candidate in economics at Harvard University.'

Schilbach, a development economist, explains that the idea for the study originated from prior research he conducted with his team in locations like Chennai. In their investigations, they observed that individuals with limited financial resources frequently encounter obstacles when attempting to get adequate sleep. This issue exacerbates the challenges these individuals already face on a daily basis.

“In Chennai, you can see people sleeping on their rickshaws,” says Schilbach, who is also a faculty affiliate at MIT’s Abdul Latif Jameel Poverty Action Lab (J-PAL). “Often, there are four or five people sleeping in the same room where it’s loud and noisy, you see people sleep in between road segments next to a highway. It’s incredibly hot even at night, and there are lots of mosquitos. Essentially, in Chennai, you can find any potential irritant or adverse sleep factor.”

The researchers utilized actigraphs, which are wristwatch-like devices that determine sleep states from body movements, to conduct their study on Chennai residents. This approach enabled the team to observe individuals in their natural home environments, unlike many other sleep studies that observe participants in laboratory settings.

During the study, 452 individuals were observed for a period of one month. The participants were divided into two groups; one group was provided with encouragement and sleep improvement tips, while the other group received financial incentives to increase their sleep duration. Additionally, some members from both groups were allowed to take daytime naps, which were monitored to determine their impact on sleep quality.

Moreover, to analyze the impact of sleep on worker productivity and earnings, the participants were assigned flexible data-entry jobs during the course of the study. This allowed the researchers to closely examine the relationship between sleep and work performance on a detailed level.

Overall, the Chennai study, the average nightly sleep duration of participants prior to the intervention was around 5.5 hours. After the intervention, the participants experienced an increase in sleep duration by an average of 27 minutes per night.

However, to achieve this increase, the participants spent an additional 38 minutes in bed per night. The participants' sleep was further hampered by their fragmented sleep patterns, with an average of 31 wake-ups per night.

According to Schilbach, one of the study's researchers, a noteworthy finding is the low sleep efficiency among participants, with very few periods of deep sleep, which is essential for restorative benefits.

Despite spending more time in bed due to the intervention, the participants' sleep quality remained unchanged, and the increase in sleep quantity was mainly due to the additional time spent in bed.

Individuals did not experience any significant improvements despite sleeping more, based on various metrics, according to the researchers. Instead, they encountered a negative effect on their working hours, as Schilbach pointed out. If they spent more time sleeping, they had less time for other aspects of their life.

On the contrary, those study participants who were given permission to nap during their data-entry job performed better in several measured categories.

“In contrast to the night sleep intervention, we find clear evidence of naps improving a range of outcomes, including their productivity, their cognitive function, and their psychological well-being, as well as some evidence on savings,” Schilbach says. “These two interventions have different effects.”

On one hand, naps were found to have a positive effect on the overall income of workers who took a break. However, it should be noted that nappers tended to be more productive per minute worked but spent less time on actual work, which did not lead to an increase in their total income.

“It’s not the case that naps just pay for themselves,” Schilbach says. “People don’t actually stay longer in the office when they nap, presumably because they have other things to do, such as taking care of their families. If people nap for about half an hour, their hours worked falls by almost half an hour, almost a one-to-one ratio, and as a result, people’s earnings in that group are lower.”

Schilbach expresses his desire for other researchers to delve into the other issues that have been raised by the study. To determine whether improved sleep quality, in addition to increased sleep quantity, has an effect, further research could seek to modify the sleeping conditions of low-wage workers.

Schilbach suggests that understanding the psychological challenges that poor people face when it comes to sleep is crucial.

“Being poor is very stressful, and that might interfere with people’s sleep,” he notes. “Addressing how environmental and psychological factors affect sleep quality is something worth examining.”

Moreover, Schilbach suggests that by utilizing actigraph technology and other devices, researchers can conduct more studies that observe people's sleep patterns in their natural homes instead of just medical facilities.

“There’s not a lot of work studying people’s sleep in their everyday lives,” Schilbach says. “And I really hope people will study sleep more in developing countries and poor countries, focusing on outcomes that people value.”

Schilbach would really like to further his sleep research in the United States, in addition to the extensive research he has conducted in India. He emphasizes the significance of sleep as an essential component of anti-poverty research and public policy, as well as a vital aspect of overall well-being, irrespective of the setting.

“Sleep might be important as an avenue for improved productivity or other types of choices people make,” Schilbach says. “But I think a good night’s sleep is also important in and of itself. We should value being able to afford to sleep well and not be worried at night. Poverty indices are about income and material consumption. But now that we can measure sleep better, a good night’s sleep should be part of a more comprehensive measure of people’s well-being. I hope that’s where we’re going eventually.”

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